Adds the necessary call-outs to allow implementation of video generation.

Machines/AppleII/AppleII.cpp

@@ -47,23 +47,58 @@ class ConcreteMachine:
 			return nullptr;
 		}
 
-		void run_for(const Cycles cycles) override {
-			m6502_.run_for(cycles);
+		Cycles perform_bus_operation(CPU::MOS6502::BusOperation operation, uint16_t address, uint8_t *value) {
+			++ cycles_since_video_update_;
+
+			switch(address) {
+				default:
+					if(isReadOperation(operation)) {
+						if(address < sizeof(ram_)) {
+							*value = ram_[address];
+						} else if(address >= rom_start_address_) {
+							*value = rom_[address - rom_start_address_];
+						} else {
+							switch(address) {
+								default:	*value = 0xff;	break;
+								case 0xc000:
+									// TODO: read keyboard.
+									*value = 0;
+								break;
+							}
+						}
+					} else {
+						if(address < sizeof(ram_)) {
+							update_video();	// TODO: be more selective.
+							ram_[address] = *value;
+						}
+					}
+				break;
+
+				case 0xc050:	update_video();		video_->set_graphics_mode();	break;
+				case 0xc051:	update_video();		video_->set_text_mode();		break;
+				case 0xc052:	update_video();		video_->set_mixed_mode(false);	break;
+				case 0xc053:	update_video();		video_->set_mixed_mode(true);	break;
+				case 0xc054:	update_video();		video_->set_video_page(0);		break;
+				case 0xc055:	update_video();		video_->set_video_page(1);		break;
+				case 0xc056:	update_video();		video_->set_low_resolution();	break;
+				case 0xc057:	update_video();		video_->set_high_resolution();	break;
+			}
+
+			// The Apple II has a slightly weird timing pattern: every 65th CPU cycle is stretched
+			// by an extra 1/7th. That's because one cycle lasts 3.5 NTSC colour clocks, so after
+			// 65 cycles a full line of 227.5 colour clocks have passed. But the high-rate binary
+			// signal approximation that produces colour needs to be in phase, so a stretch of exactly
+			// 0.5 further colour cycles is added.
+			cycles_into_current_line_ = (cycles_into_current_line_ + 1) % 65;
+			if(!cycles_into_current_line_) {
+				// Do something. Do something else.
+			}
+
+			return Cycles(1);
 		}
 
-		Cycles perform_bus_operation(CPU::MOS6502::BusOperation operation, uint16_t address, uint8_t *value) {
-			if(isReadOperation(operation)) {
-				if(address < sizeof(ram_)) {
-					*value = ram_[address];
-				} else if(address >= rom_start_address_) {
-					*value = rom_[address - rom_start_address_];
-				}
-			} else {
-				if(address < sizeof(ram_)) {
-					ram_[address] = *value;
-				}
-			}
-			return Cycles(1);
+		void flush() {
+			update_video();
 		}
 
 		bool set_rom_fetcher(const std::function<std::vector<std::unique_ptr<std::vector<uint8_t>>>(const std::string &machine, const std::vector<std::string> &names)> &roms_with_names) override {
@@ -80,9 +115,19 @@ class ConcreteMachine:
 			return true;
 		}
 
+		void run_for(const Cycles cycles) override {
+			m6502_.run_for(cycles);
+		}
+
 	private:
 		CPU::MOS6502::Processor<ConcreteMachine, false> m6502_;
 		std::unique_ptr<AppleII::Video> video_;
+		int cycles_into_current_line_ = 0;
+		Cycles cycles_since_video_update_;
+
+		void update_video() {
+			video_->run_for(cycles_since_video_update_.flush());
+		}
 
 		uint8_t ram_[48*1024];
 		std::vector<uint8_t> rom_;

Machines/AppleII/Video.cpp

@@ -11,7 +11,7 @@
 using namespace AppleII;
 
 Video::Video() :
-	crt_(new Outputs::CRT::CRT(65, 1, Outputs::CRT::DisplayType::NTSC60, 1)) {
+	crt_(new Outputs::CRT::CRT(455, 1, Outputs::CRT::DisplayType::NTSC60, 1)) {
 
 	// Set a composite sampling function that assumes 1bpp input, and uses just 7 bits per byte.
 	crt_->set_composite_sampling_function(
@@ -30,3 +30,30 @@ Video::Video() :
 Outputs::CRT::CRT *Video::get_crt() {
 	return crt_.get();
 }
+
+void Video::run_for(const Cycles) {
+}
+
+void Video::set_graphics_mode() {
+	printf("Graphics mode\n");
+}
+
+void Video::set_text_mode() {
+	printf("Text mode\n");
+}
+
+void Video::set_mixed_mode(bool mixed_mode) {
+	printf("Mixed mode: %s\n", mixed_mode ? "true" : "false");
+}
+
+void Video::set_video_page(int page) {
+	printf("Video page: %d\n", page);
+}
+
+void Video::set_low_resolution() {
+	printf("Low resolution\n");
+}
+
+void Video::set_high_resolution() {
+	printf("High resolution\n");
+}

Machines/AppleII/Video.hpp

@@ -21,6 +21,21 @@ class Video {
 		/// @returns The CRT this video feed is feeding.
 		Outputs::CRT::CRT *get_crt();
 
+		/*!
+			Advances time by @c cycles; expects to be fed by the CPU clock.
+			Implicitly adds an extra half a colour clock at the end of every
+			line.
+		*/
+		void run_for(const Cycles);
+
+		// Inputs for the various soft switches.
+		void set_graphics_mode();
+		void set_text_mode();
+		void set_mixed_mode(bool);
+		void set_video_page(int);
+		void set_low_resolution();
+		void set_high_resolution();
+
 	private:
 		std::unique_ptr<Outputs::CRT::CRT> crt_;
 };